Mistake on this page?
Report an issue in GitHub or email us


Use the DigitalInOut interface as a bidirectional digital pin:

  • Read the value of a digital pin when set as an input().
  • Write the value when set as an output().

You can use any of the numbered Arm Mbed pins as a DigitalInOut.

Note: Some platforms have a time delay when switching between input and output.

DigitalInOut class reference

Public Member Functions
 DigitalInOut (PinName pin)
 Create a DigitalInOut connected to the specified pin. More...
 DigitalInOut (PinName pin, PinDirection direction, PinMode mode, int value)
void write (int value)
int read ()
void output ()
 Set as an output. More...
void input ()
 Set as an input. More...
void mode (PinMode pull)
 Set the input pin mode. More...
int is_connected ()
DigitalInOutoperator= (int value)
 A shorthand for write() More...
DigitalInOutoperator= (DigitalInOut &rhs)
 A shorthand for write() using the assignment operator which copies the state from the DigitalInOut argument. More...
 operator int ()
 A shorthand for read() More...

DigitalInOut hello, world

 * SPDX-License-Identifier: Apache-2.0

#include "mbed.h"

DigitalInOut mypin(LED1);

int main()
    // check that mypin object is initialized and connected to a pin
    if (mypin.is_connected()) {
        printf("mypin is initialized and connected!\n\r");

    // Optional: set mode as PullUp/PullDown/PullNone/OpenDrain

    while (1) {
        // write to pin as output
        mypin = !mypin; // toggle output

        // read from pin as input
        printf("mypin.read() = %d \n\r", mypin.read());

Important Information for this Arm website
